PROJECT SUMMARY/ABSTRACT Impact: Over 40 million Americans suffer from hypertension. Timely diagnosis and control of high arterial blood pressure (AP) are crucial for preventing life-threatening complications and end-organ damage but have been hampered by the lack of nondisruptive monitors for 24-hour (including essential nighttime) AP tracking. Due to the epidemic proportions of AP abnormalities, an unobtrusive, cuff-free AP monitor will have a significant, lasting impact on the lives of millions of Americans, particularly those with cardiovascular risk factors and chronic cardiovascular diseases. Background: In Phase 1, we developed a working prototype of the AP Expert (APEX), a system for nonobtrusive (cuff-free) tracking of the AP waves in central arteries using a multisensor array and personalized calibration. The system was tested alongside a clinical oscillometric system in 30 human subjects and met the requirements of the AAMI standards, surpassing the accuracy of several commercial systems. In addition, the signal quality was tested in overnight studies in a real-life setting (at home) and found acceptable for AP tracking. Goal: The goal of Phase 2 of this project is to refine the prototype system for nonobtrusive AP tracking and to test it in larger human studies. In Aim 1, the system?s overnight performance in the course of sleep studies will be tested. In Aim 2, the system?s performance will be tested alongside a standard intra-arterial line in cardiac ICU (CICU) patients to determine optimal number of calibration points and to refine the signal-processing algorithm based on these data. In Aim 3, the prototype will be further refined to improve the sensors? durability, performance and form factor. The expected outcome of Phase 2 is a clinical-grade, mobile system for nighttime AP tracking.